United Nations Secretary General Antonio Guterres has called for the implementation of Iran’s nuclear deal based on its “mechanisms,” stressing that it must be preserved.

“The (nuclear deal) constitutes a major achievement of nuclear non-proliferation and diplomacy, and has contributed to regional and international peace and security,” said Guterres’ spokesman, Stephane Dujarric, on Wednesday.

He added that the Joint Comprehensive Plan of Action (JCPOA) “should be addressed without prejudice to preserving the agreement.”

Speaking on behalf of the UN chief, Dujarric added that issues related to the JCPOA must be “addressed through the mechanisms established by the agreement.”

The remarks were made after US President Donald Trump’s recent attempts to change Iran’s nuclear deal with the world powers.

On Friday, Trump extended waivers of economic sanctions on Iran for another 120 days but said he was doing so “for the last time.”

Trump said he wanted Congress to pass a bill requiring “timely, sufficient, and immediate inspections” at all sites by inspectors of International Atomic energy Agency (IAEA), and the indefinite extension of limits on Iran’s uranium enrichment and other nuclear activities.

“Despite my strong inclination, I have not yet withdrawn the United States from the Iran nuclear deal. Instead, I have outlined two possible paths forward: either fix the deal’s disastrous flaws, or the United States will withdraw,” Trump said in a statement.

Iran and the five permanent members of the United Nations Security Council – the United States, France, Britain, Russia and China – plus Germany signed the Joint Comprehensive Plan of Action (JCPOA) on July 14, 2015 and started implementing it on January 16, 2016.

Under the JCPOA, Iran undertook to put limits on its nuclear program in exchange for the removal of nuclear-related sanctions imposed against Tehran.